title: Patients who undergo preoperative chemoradiotherapy for locally advanced rectal cancer restaged by using diagnostic MR imaging: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To obtain performance values of magnetic resonance (MR) imaging for restaging locally advanced rectal cancer after neoadjuvant treatment regarding tumor staging, nodal staging, and tumor-free circumferential resection margins (CRMs).
  
  
  METHODS
  MEDLINE, EMBASE, and Cochrane databases were searched for studies regarding restaging compared with a reference standard by using the terms rectal neoplasms, MR imaging, and chemotherapy. The Quality Assessment of Diagnostic Accuracy Studies tool was used, and data on imaging criteria, histopathologic criteria, and restaging were extracted. Responders were defined as positives and nonresponders, as negatives. Mean sensitivity, mean specificity, and positive and negative likelihood ratios (LRs) were determined by using a bivariate random-effects model. A positive LR greater than 5 implied moderate results for responders.
  
  
  RESULTS
  Thirty-three studies evaluated 1556 patients. For tumor stage, mean sensitivity was 50.4%, mean specificity was 91.2%, positive LR was 5.76, and negative LR was 0.54. Diffusion-weighted (DW) imaging showed comparable positive LR with significantly improved sensitivity (P = .01) and negative LR (P = .04). Experienced observers showed higher sensitivity (P = .01) and lower negative LR (P = .03) compared with less experienced observers. For CRM, mean sensitivity, mean specificity, positive LR, and negative LR were 76.3%, 85.9%, 5.40, and 0.28, respectively. For nodal stage per patient, mean sensitivity, mean specificity, positive LR, and negative LR were 76.5%, 59.8%, 1.90, and 0.39, respectively; and for nodal stage on a lesion basis, these values were 90.7%, 73.0%, 3.37, and 0.13, respectively.
  
  
  CONCLUSIONS
  MR imaging showed heterogeneous results of diagnostic performances for restaging rectal cancer after neoadjuvant treatment, but significantly better results were demonstrated when DW imaging was used or with experienced observers. MR imaging can also be used for evaluation of CRM staging, but nodal staging remains challenging.
authors.affiliation: Department of Radiology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands.
authors.forename: Marije P
authors.initials: MP
authors.lastname: van der Paardt
authors.forename: Marjolein B
authors.initials: MB
authors.lastname: Zagers
authors.forename: Regina G H
authors.initials: RG
authors.lastname: Beets-Tan
authors.forename: Jaap
authors.initials: J
authors.lastname: Stoker
authors.forename: Shandra
authors.initials: S
authors.lastname: Bipat
mesh_terms: D059248:Chemoradiotherapy / Q000706:statistics & numerical data*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D009367:Neoplasm Staging; D011300:Preoperative Care / Q000706:statistics & numerical data*; D015995:Prevalence; D011379:Prognosis; D012004:Rectal Neoplasms / Q000453:epidemiology / Q000473:pathology* / Q000628:therapy*; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D016896:Treatment Outcome